The present invention relates to a rodless cylinder unit with brake for stopping sliding table and used for operating members of various types of machines.
The present inventors previously invented a rodless cylinder unit with brake as shown in FIGS. 24 to 26. The patent application was filed at the Japanese Patent Office on Feb. 22, 1991 and was received as the Japanese Patent Application No. 3-50508. Description is now given on a rodless cylinder unit with brake shown in FIGS. 24 to 26, which is not laid open and not known in the art before the application was filed. On both ends of a cylinder tube (main base) 1, a first head cover 4 and a second head cover 5 are mounted, and a slider 2 is slidably supported on the cylinder tube 1 through a guide. The slider 2 is moved by a rodless cylinder 35 of the cylinder tube 1. On top of the slider 2, a table 3 is mounted. Air chamber is formed on the table 3, and brake chambers 10 and 11 are provided on top of the slider 2 below the air chamber. Brake bands 8 and 9 are inserted into the brake chambers 10 and 11 and placed above the cylinder tube 1, and both ends of the brake bands 8 and 9 are fixed on the first head cover 4 and the second head cover 5. In the brake chambers 10 and 11, brake shoes 14 and 15 are mounted above and below the brake bands 8 and 9. On top surface of the upper brake shoe 14, a plate 200 is abutted, and the lower brake shoe 15 is fixed on bottom surface on the brake chambers 10 and 11. A diaphragm device 32 is provided in the air chamber, dividing the air chamber into an upper air chamber 25 and a lower air chamber 26. Between the diaphragm device 32 and top surface of the upper air chamber 25, springs 30 and 31 are provided, and the springs 30 and 31 apply downward resilient force on the diaphragm device 32. On lower surface of the diaphragm device 32, rods 201 and 202 are fixed, and lower end of the rods 201 and 202 are abutted on the plate 200. When the brake is released, the plate 200 is pushed upward by a return spring 203.
On both sides of lower portion of the rodless cylinder 35 in the cylinder tube 1, a passage 204 and a guide groove 205 are formed along the cylinder tube on almost the same horizontal plane. As shown in FIG. 25, the right end of the passage 204 is communicated with a passage 208 of the first head cover 4. A port 206 is provided on the right end of the passage 208, and the left end of the passage 204 is communicated with a U-shaped passage 207 in the second head cover 5. A hollow air supply piston 209 is slidably and airtightly inserted into the passage 204. One end of a flexible air tube 211 is connected to an air passage 210 of the air supply piston 209, and the air tube 211 extends into the guide groove 205 through the U-shaped passage 207. As shown in FIG. 24, an adaptor 212 with L-shaped cross-section is connected to left lower end of the slider 2, and one end of the adaptor 212 is inserted into the guide groove 205 on non-contact basis, and it moves in the guide 205 as the slider 2 is moved. A passage 213 is formed in the adaptor 212. One end of the passage 213 is communicated with the lower air chamber 26 through a passage 40 in the slider 2, and the other end of the passage 213 is connected to the other end of the air tube 211 through a joint 214. Thus, the lower air chamber 26 and the port 206 are communicated with each other.
In the conventional type rodless cylinder unit with brake not laid-open, an axial passage is provided in the cylinder tube as described above, and a tube for supplying and discharging pressure fluid is provided in this passage along axial direction of the cylinder tube. One end of the tube is connected to the sliding table, and the other end of the tube is mounted on the air supply piston, which is closely slided in said passage. Therefore, it is disadvantageous in that a passage for providing the tube is required and that friction occurs when the tube and the air supply piston are slided in the passage. Also, the position of the air supply piston changes according to the position of the sliding table, and the length of the passage for air supply also varies. The time required from operation of directional control valve for air supply up to the arrival of the air to the brake of the rodless cylinder varies according to the position of the sliding table.
Also, in the conventional type rodless cylinder unit with brake, brake is maintained in release state during initial adjustment of the rodless cylinder unit with brake, and the air under pressure higher than a predetermined pressure value must be continuously supplied to the air chamber in the sliding table. This results in waste of energy when long time is required for initial adjustment of rodless cylinder with brake. Also, there is restriction in terms of operation because the air is continuously supplied to the air chamber.